It is well known in the art that petroleum-based fluids, such as crude oil, have viscosity characteristics of liquid suspensions or emulsions. As a result, the three basic types of crude oil—paraffin-based, asphalt-based, and mixed-base (paraffin-based and asphalt-based mixed)—all exhibit the characteristic of increased viscosity corresponding to decreased fluid temperatures. In paraffin-based crude oil, as the temperature of the fluid decreases, especially when the temperature falls just below the temperature at which wax begins to precipitate (called the wax-appearance temperature), paraffin in the fluid crystallizes into many nanometer-sized particles which suspend in the solvent and increase the apparent viscosity of the fluid. In asphalt-based crude oil, asphalt in the fluid solidifies into an increasing number of asphaltene particles as the temperature decreases, resulting in a continuous increase in apparent viscosity. Mixed-based crude oil likewise demonstrates an inverse viscosity/temperature relationship similar to characteristics of both paraffin-based and asphalt-based crude oils. This inverse viscosity/temperature relationship is particularly problematic when the increase in viscosity fouls pipelines in which crude oil is transported.
In addition to the viscosity increase at lower temperatures, crude oil precipitates wax or asphaltene particles at lower temperatures, which is particularly problematic because of its detrimental effect on the transportation of crude oil via pipeline. As a result of crude oil wax or asphaltene precipitation, pipelines must be frequently shut down and cleaned to scrape out wax or asphaltene buildup in the piping to prevent obstruction of crude oil flow.
With increasing demands on world oil supplies and the low temperature climates, for example offshore oil wells and the Artic and sub-Arctic environs, in which oil is extracted or through which it is transported, it is increasingly important to develop methods for improving the flow of crude oil in pipelines at lower temperatures.
For the reasons described above, a method for decreasing viscosity and facilitating fluid flow of petroleum-based fluids, such as crude oil, is desirable.